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app.py

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+
+"""
+Flask Login System with SQLite
+Features:
+- Signup (create new account)
+- Login (check user credentials)
+- Session (to remember login state)
+- Cookies (to store last visit info)
+- "Remember Me" option (stay logged in even after closing browser)
+"""
+
+from flask import Flask, render_template, request, redirect, url_for, session, make_response
+import sqlite3
+from datetime import timedelta
+
+# Flask App Setup
+app = Flask(__name__)
+
+# Secret key is used to sign session data (must be kept secret in real apps!)
+app.secret_key = "supersecretkey"
+
+# Permanent sessions last for 7 days (used when "Remember Me" is checked)
+app.permanent_session_lifetime = timedelta(days=7)
+
+
+# Helper function to connect to SQLite database
+def get_db_connection():
+    # Connect to SQLite database (creates file users.db if it doesn’t exist)
+    conn = sqlite3.connect("users.db")
+    conn.row_factory = sqlite3.Row  # Makes rows behave like dictionaries
+    return conn
+
+
+# Initialize database with a "users" table
+def init_db():
+    conn = get_db_connection()
+    conn.execute("""
+        CREATE TABLE IF NOT EXISTS users (
+            id INTEGER PRIMARY KEY AUTOINCREMENT, -- Auto-increment ID
+            username TEXT UNIQUE NOT NULL,        -- Unique username
+            password TEXT NOT NULL                -- Password (plain text for demo, should use hashing!)
+        )
+    """)
+    conn.commit()
+    conn.close()
+
+# Call database initialization at startup
+init_db()
+
+
+# Home Page (only logged-in users can see this)
+@app.route("/")
+def home():
+    # Check if the user is logged in using session
+    if "username" in session:
+        username = session["username"]  # Get logged-in username from session
+
+        # Get last visit message from cookie (if not found, show default message)
+        last_visit = request.cookies.get("last_visit", "First time visiting!")
+
+        return render_template("home.html", username=username, last_visit=last_visit)
+
+    # If not logged in, redirect to login page
+    return redirect(url_for("login"))
+
+
+# Signup Page
+@app.route("/signup", methods=["GET", "POST"])
+def signup():
+    if request.method == "POST":  # When user submits the form
+        username = request.form["username"]
+        password = request.form["password"]
+
+        conn = get_db_connection()
+        try:
+            # Insert new user into database
+            conn.execute("INSERT INTO users (username, password) VALUES (?, ?)", (username, password))
+            conn.commit()
+            conn.close()
+
+            # After signup, redirect to login page
+            return redirect(url_for("login"))
+
+        except sqlite3.IntegrityError:
+            # This happens if the username already exists
+            return "Username already exists! Try another."
+    
+    # If GET request, show signup form
+    return render_template("signup.html")
+
+
+# Login Page
+@app.route("/login", methods=["GET", "POST"])
+def login():
+    if request.method == "POST":  # When user submits login form
+        username = request.form["username"]
+        password = request.form["password"]
+
+        # Checkbox value: will be "on" if user ticks "Remember Me"
+        remember = request.form.get("remember")
+
+        # Check if username & password exist in database
+        conn = get_db_connection()
+        user = conn.execute("SELECT * FROM users WHERE username=? AND password=?", 
+                            (username, password)).fetchone()
+        conn.close()
+
+        if user:
+            # ✅ User found → start session
+            if remember == "on":
+                # Session will survive browser close (7 days)
+                session.permanent = True
+            else:
+                # Session ends when browser closes
+                session.permanent = False
+
+            # Store username inside session
+            session["username"] = username
+
+            # Create response with cookie
+            resp = make_response(redirect(url_for("home")))
+
+            # Save a cookie with "last visit" info
+            # If "Remember Me" checked → cookie valid for 7 days
+            # Else → cookie lasts only until browser closes
+            resp.set_cookie("last_visit", "Welcome back, " + username, 
+                            max_age=(7*24*60*60 if remember == "on" else None))
+
+            return resp
+        else:
+            # If username or password is wrong
+            return "Invalid username or password. Try again."
+
+    # If GET request, show login form
+    return render_template("login.html")
+
+
+# Logout Page
+@app.route("/logout")
+def logout():
+    # Remove username from session
+    session.pop("username", None)
+
+    # Also delete the "last_visit" cookie
+    resp = make_response(redirect(url_for("login")))
+    resp.set_cookie("last_visit", "", expires=0)
+    return resp
+
+
+# Run the App
+if __name__ == "__main__":
+    app.run(debug=True, host="0.0.0.0", port=5000)

readme.md

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+# 🔑 Flask Login System with SQLite
+
+A **beginner-friendly** login & signup system using **Flask** and **SQLite**.  
+This project demonstrates:
+
+- ✅ User Signup (create a new account)  
+- ✅ User Login (check credentials)  
+- ✅ Session Management (keep users logged in)  
+- ✅ Cookies (store "last visit" info)  
+- ✅ "Remember Me" option (stay logged in even after closing browser)  
+
+---
+
+## 📂 Project Structure
+
+```
+
+/project-folder
+│── app.py              # Main Flask application
+│── users.db            # SQLite database (auto-created)
+│── templates/
+│    ├── home.html      # Home page (only for logged-in users)
+│    ├── login.html     # Login form
+│    └── signup.html    # Signup form
+
+````
+
+---
+
+## ⚡ Installation & Setup
+
+### 1️⃣ Clone or Download
+```bash
+git clone https://github.com/yourusername/flask-login-system.git
+cd flask-login-system
+````
+
+### 2️⃣ Create Virtual Environment (recommended)
+
+```bash
+python -m venv venv
+source venv/bin/activate   # On Mac/Linux
+venv\Scripts\activate      # On Windows
+```
+
+### 3️⃣ Install Dependencies
+
+```bash
+pip install flask
+```
+
+### 4️⃣ Run the App
+
+```bash
+python app.py
+```
+
+Flask will start at:
+👉 [http://127.0.0.1:5000/](http://127.0.0.1:5000/)
+
+---
+
+## 🖥️ Usage
+
+1. Open `http://127.0.0.1:5000/signup`
+
+   * Create a new account.
+
+2. Go to `http://127.0.0.1:5000/login`
+
+   * Enter username & password.
+   * Tick **Remember Me** if you want to stay logged in after closing browser.
+
+3. After login → you’ll be redirected to **Home Page**.
+
+   * It will also show your **last visit info** stored in cookies.
+
+4. To logout → go to `http://127.0.0.1:5000/logout`.
+
+---
+
+## 🍪 How It Works
+
+* **Sessions**
+
+  * Store who is logged in (`session["username"]`).
+  * By default, session ends when browser is closed.
+  * If "Remember Me" is checked → session lasts **7 days**.
+
+* **Cookies**
+
+  * Store a `last_visit` message.
+  * If "Remember Me" is checked → cookie also lasts **7 days**.
+  * Otherwise, cookie disappears when browser closes.
+
+---
+
+## ⚠️ Security Notes (for teaching only!)
+
+* Passwords are stored in **plain text** in this demo (❌ not secure).
+* In real applications → **always hash passwords** using libraries like `werkzeug.security` or `bcrypt`.
+
+---
+
+## ✨ Future Improvements
+
+* Add **password hashing** for security
+* Add **email verification / password reset**
+* Use **Flask-Login** for better authentication management
+
+---
+
+## 👨‍💻 Author
+
+Created as a **teaching project for extreme beginners** learning Flask, Sessions, and Cookies.
+
+
+---

static/space-theme.css

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+body {
+    margin: 0;
+    padding: 0;
+    min-height: 100vh;
+    font-family: 'Segoe UI', Arial, sans-serif;
+    background: #0b0c2a;
+    color: #fff;
+    position: relative;
+    overflow: hidden;
+}
+.stars {
+    position: absolute;
+    width: 100%;
+    height: 100%;
+    top: 0; left: 0;
+    z-index: 0;
+}
+.star {
+    position: absolute;
+    background: white;
+    border-radius: 50%;
+    opacity: 0.8;
+    animation: twinkle 2s infinite alternate;
+}
+@keyframes twinkle {
+    from { opacity: 0.5; }
+    to { opacity: 1; }
+}
+.container {
+    position: relative;
+    z-index: 1;
+    max-width: 400px;
+    margin: 100px auto;
+    background: rgba(20, 24, 60, 0.85);
+    border-radius: 16px;
+    box-shadow: 0 0 30px #1a1a40;
+    padding: 40px 30px;
+    text-align: center;
+}
+h2 {
+    margin-bottom: 20px;
+    font-size: 2em;
+    letter-spacing: 2px;
+}
+p {
+    margin-bottom: 30px;
+    font-size: 1.1em;
+}
+a {
+    display: inline-block;
+    padding: 10px 30px;
+    background: #4e54c8;
+    color: #fff;
+    border-radius: 25px;
+    text-decoration: none;
+    font-weight: bold;
+    transition: background 0.3s;
+}
+a:hover {
+    background: #8f94fb;
+}

templates/home.html

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+<!DOCTYPE html>
+<html>
+<head>
+    <title>Home</title>
+    <link rel="stylesheet" href="{{ url_for('static', filename='space-theme.css') }}">
+</head>
+<body>
+    <div class="stars">
+        <div class="star" style="top: 10%; left: 20%; width: 2px; height: 2px;"></div>
+        <div class="star" style="top: 30%; left: 70%; width: 3px; height: 3px;"></div>
+        <div class="star" style="top: 60%; left: 40%; width: 1.5px; height: 1.5px;"></div>
+        <div class="star" style="top: 80%; left: 80%; width: 2.5px; height: 2.5px;"></div>
+        <div class="star" style="top: 50%; left: 10%; width: 1px; height: 1px;"></div>
+        <div class="star" style="top: 20%; left: 90%; width: 2px; height: 2px;"></div>
+        <div class="star" style="top: 75%; left: 55%; width: 1.5px; height: 1.5px;"></div>
+        <div class="star" style="top: 40%; left: 60%; width: 2.5px; height: 2.5px;"></div>
+    </div>
+    <div class="container">
+    <h2>Welcome, {{ username }}!</h2>
+    <p>Last visit info (from cookie): {{ last_visit }}</p>
+    <a href="https://gagan0141.github.io/portfolio/">My Portfolio</a>
+    <a href="{{ url_for('logout') }}">Logout</a>
+    </div>
+</body>
+</html>

templates/login.html

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+<!DOCTYPE html>
+<html>
+<head>
+    <title>Login</title>
+    <link rel="stylesheet" href="{{ url_for('static', filename='space-theme.css') }}">
+</head>
+<body>
+    <div class="stars">
+        <div class="star" style="top: 10%; left: 20%; width: 2px; height: 2px;"></div>
+        <div class="star" style="top: 30%; left: 70%; width: 3px; height: 3px;"></div>
+        <div class="star" style="top: 60%; left: 40%; width: 1.5px; height: 1.5px;"></div>
+        <div class="star" style="top: 80%; left: 80%; width: 2.5px; height: 2.5px;"></div>
+        <div class="star" style="top: 50%; left: 10%; width: 1px; height: 1px;"></div>
+        <div class="star" style="top: 20%; left: 90%; width: 2px; height: 2px;"></div>
+        <div class="star" style="top: 75%; left: 55%; width: 1.5px; height: 1.5px;"></div>
+        <div class="star" style="top: 40%; left: 60%; width: 2.5px; height: 2.5px;"></div>
+    </div>
+    <div class="container">
+    <h2>Login</h2>
+    <form method="POST">
+        <label>Username:</label>
+        <input type="text" name="username" required><br><br>
+
+        <label>Password:</label>
+        <input type="password" name="password" required><br><br>
+
+        <label>
+            <input type="checkbox" name="remember"> Remember Me
+        </label><br><br>
+
+        <button type="submit">Login</button>
+    </form>
+    <p>Don't have an account? <a href="{{ url_for('signup') }}">Signup here</a></p>
+    </div>
+</body>
+</html>

templates/signup.html

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+<!DOCTYPE html>
+<html>
+<head>
+    <title>Signup</title>
+    <link rel="stylesheet" href="{{ url_for('static', filename='space-theme.css') }}">
+</head>
+<body>
+    <div class="stars">
+        <div class="star" style="top: 10%; left: 20%; width: 2px; height: 2px;"></div>
+        <div class="star" style="top: 30%; left: 70%; width: 3px; height: 3px;"></div>
+        <div class="star" style="top: 60%; left: 40%; width: 1.5px; height: 1.5px;"></div>
+        <div class="star" style="top: 80%; left: 80%; width: 2.5px; height: 2.5px;"></div>
+        <div class="star" style="top: 50%; left: 10%; width: 1px; height: 1px;"></div>
+        <div class="star" style="top: 20%; left: 90%; width: 2px; height: 2px;"></div>
+        <div class="star" style="top: 75%; left: 55%; width: 1.5px; height: 1.5px;"></div>
+        <div class="star" style="top: 40%; left: 60%; width: 2.5px; height: 2.5px;"></div>
+    </div>
+    <div class="container">
+    <h2>Signup</h2>
+    <form method="POST">
+        <label>Username:</label>
+        <input type="text" name="username" required><br><br>
+
+        <label>Password:</label>
+        <input type="password" name="password" required><br><br>
+
+        <button type="submit">Signup</button>
+    </form>
+    <p>Already have an account? <a href="{{ url_for('login') }}">Login here</a></p>
+    </div>
+</body>
+</html>